Mixin.dart

class Hero extends Character {
  String hitMonster() {
    return 'Take this..!';
  }
}

!------------------------------------------------------

mixin DrinkAbility on Hero{
  String drink() => 'gluk...gluk...gluk...';
}

!------------------------------------------------------

class Knight extends Hero with DrinkAbility{

}

!------------------------------------------------------

class main(List<String> arguments) {
   Knight k = Knight();
   print(k.drink() + 'is hero');
}